Method for obtaining copper from cupriferous arsenosulphide and/or antimony sulphide ores or ore concentrates

ABSTRACT

Process for extracting copper from copper-bearing arsenic sulfide and/or antimony sulfide ores, ore concentrates or minerals, comprising the following steps:
         converting the ores, ore concentrates or minerals by reaction with sulfur at 300 to 600° C. for at least 5 min;   grinding the reaction product;   physically separating the arsenic and/or antimony sulfides obtained at least partially from copper-containing sulfides;   treating the separated copper-containing sulfides by pyrometallurgical or hydrometallurgical processes to obtain copper.

The present invention relates to a process for extracting copper fromcopper-bearing arsenic sulfide and/or antimony sulfide ores.

By far the biggest part of the world's copper production (about 90%) isextracted from copper sulfide minerals. Among the copper sulfideminerals, there may be mentioned, above all, chalcopyrite (CuFeS₂),bornite (Cu₅FeS₄), cubanite (CuFeS₄), chalcosine (Cu₂S), digenite(Cu₉S₅), covelline (CuS), enargite (Cu₃AsS₄), tennantite (Cu₁₂As₄S₁₃)and tetrahedrite (Cu₁₂Sb₄S₁₃).

Among the copper sulfide minerals, chalcopyrite is the most widespreadmineral; therefore, it is of the greatest scientific and economicimportance in the development of new extraction methods.

In addition, chalcopyrite and the above mentioned minerals arecharacterized by always containing deposited gold, silver, platinummetals and other rare metals as well as rare earths.

The copper/iron-sulfidic minerals are extracted from ores, which areusually milled and concentrated by a flotation process to yield an oreconcentrate, whereby a substantial part of the silicates contained inthe ground stock, in particular, is separated off.

Today, in addition to the known pyrometallurgical and chemicalhydrometallurgical processes, there are various approaches to leachingcopper and other metals occurring in the copper sulfide minerals fromthe ores or ore concentrates using hydrometallurgical bioleachingprocesses. This involves the problem that only part of the coppercontained in chalcopyrite can be leached out using the known processesbecause passivation of the chalcopyrite occurs.

Many copper-bearing ores additionally contain arsenic and antimonycompounds, for example, enargite (Cu₃AsS₄), tennantite (Cu₁₂As₄S₁₃) andtetrahedrite (Cu₁₂Sb₄S₁₃). These ores are difficult to process. Inaddition to the environmental problems occurring in the processing ofsuch ores, the arsenic and antimony contents in higher levels are alsodamaging to the plants employed in the pyrometallurgical treatment.

WO 01/44524 describes a process for extracting copper fromchalcopyrite-containing ores in which the chalcopyrite-containing oresare converted to covelline, pyrite and accompanying substances by theaddition of sulfur and then copper is extracted by leaching steps of themicrobiological or chemical type.

It was the object of the present invention to develop a process by whichthe extraction of copper from copper-bearing arsenic sulfide and/orantimony sulfide ores can be improved.

This object is achieved by a process comprising the following steps:

-   -   converting the ores, ore concentrates or minerals by reaction        with sulfur at 300 to 600° C. for at least 5 min;    -   grinding the reaction product;    -   physically separating the arsenic and/or antimony sulfides        obtained at least partially from copper-containing sulfides;    -   treating the separated copper-containing sulfides by        pyrometallurgical or hydrometallurgical processes to obtain        copper.

According to the invention, the copper-bearing arsenic sulfide and/orantimony sulfide ores, ore concentrates or minerals are converted toarsenic and/or antimony sulfides and copper-containing sulfides usingsulfur.

Then, according to the invention, arsenic and/or antimony sulfides arephysically separated from copper-containing sulfides at least partiallyat first.

Preferably, at least 70 or 90%, more preferably at least 95%, by weightof the arsenic and antimony sulfides are separated. Then, copper can beextracted from the thus purified copper sulfide using pyrometallurgicaland hydrometallurgical processes known to the skilled person, avoidingthe problems normally arising from the presence of admixed arsenic orantimony sulfides.

The separation of the copper sulfides and arsenic or antimony sulfidesis effected by grinding at first. In a preferred embodiment, theseparation can be effected by electrostatic processes, gravimetricprocesses, magnetic processes, air classification, grain size selection,a hydrocyclone, flotation processes or combinations thereof.

In one embodiment, at least two separation methods are combined.

Another possibility is the selective heating of minerals with microwavesof different frequencies in order to alter the physical properties ofindividual minerals to enable their being separated off selectively, forexample, by magnetic methods.

The ores employed according to the invention typically contain othermetal components, especially rare earths, gold, silver, platinum,cobalt, nickel, zinc. Depending on the process control, these canmigrate with either the arsenic or antimony sulfide phase or the coppersulfide phase, or be separated off in separate phases.

According to the invention, the precious metals, for example, gold andsilver, in the copper-containing phase are preferably enriched almostcompletely by a diffusion process and thus can also be recovered almostcompletely among the other copper-sulfidic minerals particularly easily.

Inasmuch as sulfur is obtained in the further processing, it may beadvantageously recycled to the starting step of the process.

In particular, the pyrometallurgical processing includes a step referredto as “smelting”. In this step, oxygen is blown into the molten materialso that the following reactions proceed:

CuS+0 ₂→Cu+SO₂.

The thus obtained Cu is then typically freed from excess oxygen byadding reducing agents. Subsequently, electrorefining may also be used.

The arsenic or antimony sulfides obtained may be used for preparingarsenic or antimony; it is also possible to dispose of them.

Preferably, the reaction is performed in an inert atmosphere. In oneembodiment, the conversion is performed in a continuous process,preferably in a three-chamber system.

The reaction may be performed in a nitrogen atmosphere, for example, butalso in argon or in a mixture of the inert gases. Flue gas may also beused, preferably SO₂.

In a preferred embodiment, the grinding process is effected in a rotarykiln or in a fluidized bed reactor in situ by adding grinding balls, forexample.

Particularly suitable for the realization is conversion in a rotary kilnor fluidized bed reactor.

Typical reaction times are around 5 min to 24 h, preferably 5 min to 12h, or 15 min to 24 h, or 0ö6.5 h to 24 h, especially from 5 to 90 orfrom 5 to 60 min.

Temperatures from 300° C. upwards, preferably >380 ° C. or >400° C., aresuitable. The temperature is preferably <500° C., more preferably ≦475°C. or ≦<450° C. Temperatures of from 450 to 500° C. are particularlypreferred.

The reaction time is dependent on the grain size of the ores, oreconcentrates and minerals employed. Preferred values for d50 are below210 μm, such grain sizes typically being obtained in the processing ofores by flotation. Grain sizes of d50=410 μm, d50=350 μm and d50=125 μmmay also be employed.

The starting materials can be selected from copper-containing ores, oreconcentrates or minerals, such as enargite (Cu₃AsS₄), tennantite(Cu₁₂As₄S₁₃) and/or tetrahedrite (Cu₁₂Sb₄S₁₃), optionally accompanied bychalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), cubanite (CuFeS₄), chalcosine(Cu₂S), digenite (Cu₉S₅) and/or covelline (CuS).

The amount of sulfur employed can be stoichiometric, half-stoichiometricor catalytic.

Depending on the composition of the starting material, thecopper-containing sulfides obtained may be covelline, chalcosine,digenite, bornite. The arsenic and antimony sulfides are typicallyobtained as As₂S₃ or asS and Sb₂S₃ or SbS, respectively.

The reactions can be described in part by the following equations:

2 Cu₃AsS₄+0 S→6 CuS+AsS (S only catalytically)

2 Cu₃AsS₄+S→6 CuS+As₂S₃

Cu₁₂As₄S₁₃+5S→12 CuS+2As₂S₃

Cu₁₂Sb₄S₁₃+5S→12 CuS+2Sb₂S₃

If the copper ore contains iron, the following reactions take placeadditionally:

Cu₅FeS₄+3S→5 CuS+FeS₂

Cu₅FeS₄+2S→5 CuS+FeS

CuFeS2+0.5 S→CuS+FeS

EXAMPLE

FIGS. 1 a and b show the conversion of an ore by the converting stepemployed according to the invention.

FIG. 1 a shows a chalcopyrite-containing ore, and FIG. 1 b shows theconverted ore: a pyrite core with a coat of covelline. Arsenic andantimony are enriched in the pyrite.

FIGS. 2 a and b show a copper ore before and after the conversion. FIG.2 a shows the copper ore before the conversion; iron, copper andprecious metals are homogeneously distributed, and FIG. 2 b shows thecopper ore after the conversion; copper and iron are separated, and theprecious metals are enriched in the copper sulfide.

1. A process for extracting copper from copper-bearing arsenic sulfideand/or antimony sulfide ores, ore concentrates or minerals, comprisingthe following steps: converting the ores, ore concentrates or mineralsby reaction with sulfur at 300 to 600° C. for at least 5 min; grindingthe reaction product; physically separating the arsenic and/or antimonysulfides obtained at least partially from copper-containing sulfides;and treating the separated copper-containing sulfides bypyrometallurgical or hydrometallurgical processes to obtain copper. 2.The process of claim 1, wherein the conversion is performed in an inertatmosphere.
 3. The process claim 1, wherein the conversion is performedin a continuous process.
 4. The process of claim 1, wherein thetemperature is at 450° C. to 500° C.
 5. The process of claim 1, whereinthe conversion is performed in a rotary kiln or fluidized bed reactor.6. The process of claim 1, wherein the conversion is performed during aperiod of from 5 min to 12 h.
 7. The process of claim 1, wherein thetime is from 5 min to 90 min.
 8. The process of claim 1, wherein anenrichment of the precious metals in the copper-sulfidic phase takesplace during the conversion.
 9. The process of claim 1, wherein thesulfur is added in stoichiometric, half-stoichiometric or catalyticamount.
 10. The process of claim 1, wherein the antimony and/or arsenicsulfides are transferred to a processing step.
 11. The process of claim1, wherein the separation of the antimony and/or arsenic sulfides iseffected by electrostatic processes, gravimetric processes, magneticprocesses, air classification, grain size selection, hydrocyclonemethods, flotation processes or combinations thereof.
 12. The process ofclaim 1, wherein the copper-bearing arsenic sulfide and/or antimonysulfide ores, ore concentrates or minerals are selected from the groupconsisting of enargite (Cu3AsS4), tennantite (Cu12As4S13), tetrahedrite(Cu12Sb4S13), and combinations thereof, optionally accompanied bychalcopyrite (CuFeS2), bornite (Cu5FeS4), cubanite (CuFeS4), chalcosine(Cu2S), digenite (Cu9S5) and/or covelline (CuS).
 13. The process ofclaim 3, wherein the conversion is performed in a three-chamber system.14. The process of claim 6, wherein the conversion is performed during aperiod of from 5 min to 12 h.